Method: Severely diabetic albino Wister rats of same age group were
treated orally once a day upto 3wk with a dose of 400 mg/kg bw of
lyophilized extract. TG, TC, HDL, ALKP, AST, ALT and CRTN were
estimated. LDL and VLDL cholesterol levels were calculated from the
above measurements by using Friedwald formula.

Name: Indian Journal of Medical Research Publisher: Indian Council of Medical Research Audience: Academic Format: Magazine/Journal Subject: Biological sciences; Health Copyright: COPYRIGHT 2010 Indian Council of Medical
Research ISSN:0971-5916

Psidium guajava (Family: Myrtaceae) is an economically important
plant of high medicinal value (1-3). Psidium guajava is commonly known
as guava. It needs a tropical location and full sun for its healthy
growth. Flavonoids, gallic acid and tannins are invariably present in
all part of the plant viz., fruit, leaves, stem bark and heartwood
(4,5). It has been reported earlier that the polyphenols and
lucocynadines present in good amount in P. guajava may account for the
marked astringent and medicinal properties of the different parts of the
plant (4).

The guava fruit is a berry, which consists of a fleshy pericarp and
seed cavity with fleshy pulp and numerous small seeds. P. guajava fruits
are rich in dietary fiber associated with natural antioxidant compounds
(3). Recently, the ripe fruit peel has been found to posses
hyperglycaemic activity by our research group (6) and diabetic patients
are advised to peel off the ripe guava before eating. Antidiabetic
activity based on higher concentration of Mg in the raw fruit peel of P.
guajava has already been described (1,7). No reports are available on
the hypolipidaemic activity of raw fruit peel. Hence, we evaluated the
hypolipidaemic and hepatoprotective effects of raw fruit peel of P.
guajava in streptozotocin (STZ) diabetic rats.

Material & Methods

Plant material: Unripe fruits of P. guajava collected from the
guava garden Khushrobagh, Allahabad, India, were authenticated by Dr
Satya Narayan, Taxonomist, Department of Botany, University of
Allahabad, India. A voucher specimen was submitted. The raw guavas were
peeled off and the thin greenish peel of the unripe fruits was cut into
small pieces. The pieces were mechanically crushed and continuously
extracted for 48 h with hot water. The extract was filtered and
concentrated in rotatory evaporator at 35 [+ or -] 5 [degrees]C under
reduced pressure, to obtain semisolid material, which was then
lyophilized to get a powder (yield: 13.4%, w/v).

Animal care and maintenance: Experiments were performed in 6-8 wk
old, healthy, male albino Wistar rats (150-200 g). Rats obtained from
National Institute of Communicable Diseases (NICD), now National Centre
for Disease Control (NCDC), Delhi, India, were housed under standard
environmental conditions (at 25 [+ or -] 2[degrees] C, 50 [+ or -] 5%
humidity with a 12 h each of dark and light cycle) and maintained with
free access of water and a standard laboratory diet. The study protocol
was approved by the Institutional Ethical Committee.

Induction of diabetes: Diabetes was induced by a single
intraperitonial injection of freshly prepared streptozotocin (50 mg/kg
bw) in 0.1 citrate buffer (pH 4.5) to a group of overnight fasted rats.
After 3 days of STZ administration animal having marked hyperglycaemia
(fasting blood sugar, FBG> 250mg/dl) were selected for the study (1).

Experimental design: The dose of 400 mg/kg was identified as the
most effective dose in our previous study (1) and therefore selected for
the present study in case of severe diabetic rats. The animals were
divided into four groups of six rats each: Group I: normal control
placebo treated; Group II: diabetic control placebo treated; Group III:
diabetic treated with 400 mg/kg of extract; and Group IV: diabetic
treated with 250 mg/kg of tolbutamide (positive control).

All biochemical parameters were estimated initially before the
treatment and then weakly up to 21 days after the treatment.

Statistical analysis: Statistical analyses was performed using
two-way analysis of variance (ANOVA), using statistical package PRISM
3.0 version. The significance of differences between and within various
groups were determined. Differences were considered to be significant
when P<0.05.

Results & Discussion

The triglyceride levels were increased by 2.86 per cent in diabetic
control rats as compared to initial levels. However, it remained
constant in normal control. The 21 days treatment of extract resulted in
a significant (P<0.01) decrease of 47.47 per cent in TG levels of STZ
induced diabetic rats. Whereas, in positive control, the reduction
observed in TG level of rats was 48.06 per cent (Table I). The most
common lipid abnormalities in diabetes are hypertriglyceridaemia and
hypercholesterolaemia (10,11). Hypertriglyceridaemia is also associated
in metabolic consequences of hyperinsulinaemia, insulin resistance and
glucose intolerance (12). Thus, the improvement in TG levels of extract
treated group indicates the hypotriglyceridaemic potential of P. guajava
raw fruit peel and confirming thereby its usefulness for diabetic
patients.

The levels of total cholesterol (TC) of both the controls, normal
as well as diabetic, animals showed a slight increment of 1.67 and 2.86
per cent respectively, whereas, the treated diabetic animals showed a
significant (P<0.01) reduction of 19.08 per cent. The increased
levels of TC reverted back to near normal range in diabetic treated
group indicating thereby that on long term treatment the extract
produced a significant decrease in total cholesterol level. A
significant reduction of 16.03 per cent was observed in positive control
(P<0.01) compared to pretreatment level which was lesser than the
extract treated group (Table II). High density lipoprotein (HDL)
increased significantly by (P<0.001) 26.34 per cent in diabetic
treated groups which was higher than the positive control (17.53%). LDL
and VLDL levels were found to be decreased significantly by 18.84
(P<0.01) and 47.46 (P<0.001) per cent respectively in diabetic
treated group compared to pre-treatment level; increased by 12.21 and
2.55 per cent in diabetic control group, and remained constant in normal
control group. In case of positive control the fall observed was 9.42
and 48.06 per cent in LDL and VLDL levels respectively (Table II). The
risk of developing ischaemic heart disease is directly related to the
raised levels of TC, LDL, VLDL and inversely related to the HDL levels
(13,14). This extract, therefore, could be used for lowering TC,TG, LDL
and VLDL levels and reducing thereby the risk of cardiovascular diseases
by increasing HDL level.

Significant reduction (P<0.05) of 27.5 and 43.94 per cent in AST
and ALT levels respectively was observed in diabetic treated rats. In
diabetic control AST and ALT levels were increased by 10.58 and 8.64 per
cent respectively whereas, in normal control AST and ALT levels remains
constant. In the positive control group fall of 27.38 and 25 per cent in
AST and ALT levels respectively were found. Since, raised levels of AST
and ALT enzymes increase the incidence of heart and liver diseases,
decrease in their levels in diabetic treated group suggests that risk of
liver and heart diseases can be reduced in diabetic patients by eating
raw guavas. Increased level of ALKP indicates bone disease, liver
disease or bile tract blockage (14). P. guajava extract reduced ALKP
level by 25.18 per cent indicating thereby, its protective effect over
liver and improvement in liver function efficiency. These results are
comparable with the dose of Tolbutamide treated group also showed a
significant fall of 26 per cent (P<0.01). The serum creatinine level
decreased significantly (P<0.001) in treated diabetic animals by
27.27 per cent as compared to initial values. Whereas, it increased
slightly in case of controls, normal as well as diabetic, by 12.5 and
4.76 per cent respectively. Positive control showed a significant
(P<0.001) fall of 31.82 per cent in creatinine levels (Table III) .

Oral toxicity has already been checked in previous studies (1) and
the extract has been found to be relatively safe, as no mortality was
associated with the single oral administration of 6000 mg/kg of the
extract (1). Our results suggest that the raw fruit peel aqueous extract
of P. guajava showed significant hypolipidaemic and hepatoprotective
effects and will be beneficial for type 2 diabetic patients.